Refrigerant/Lubricant Mixture Boiling Heat Transfer Research at NIST.
Refrigerant/Lubricant Mixture Boiling Heat Transfer
Research at NIST.
Kedzierski, M. A.
Future Trends in Mechanical Engineering, Research and
Development, 16th National Convention of Mechanical
Engineers and All India Seminar. Proceedings.
September 29-30, 2000, 24-29 pp, 2000.
refrigerants; lubricants; heat transfer
This paper overviews the boiling heat transfer research
of the recent few years at NIST (National Institute of
Standards and Technology) on refrigerant/lubricant
mixtures. The aim of the research was to fundamentally
understand the effects of lubricant properties and
bubble parameters on heat transfer performance. The
magnitude of the effect of lubricant viscosity,
miscibility, and concentration on the heat transfer has
been quantified. The mechanistic cause of each effect
was given based on a new theoretical interpretation
and/or one from the literature. The NIST research
illustrates that large improvements over pure Rl34a heat
transfer can be obtained for Rl34a/lubricant mixtures
with small lubricant mass fraction, high lubricant
viscosity and a large critical solution temperature
(CST). A mechanistic explanation for the observed
R134a/lubricant boiling is provided. A fluorescence
measurement technique is currently under development
with the purpose of unlocking the mechanisms of the
lubricant excess layer.